Sorption and desorption of atrazine by three bacterial species isolated from aquatic systems

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Abstract
The isolatesAcinetobacter spec., Cytophaga spec. andPseudomonas fluorescens represent different morphological and physiological types of bacteria. They accumulate atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-5-triazine) to different levels. Accumulation expressed by the ratio of atrazine sorbed per volume of bacteria to atrazine per the same volume of water amounted to 11 forAcinetobacter spec., 8.6 forCytophaga spec and 6.2 forPseudomonas fluorescens. Accumulation ratios were proportional to the surface areas of the organisms. Single cells ofAcinetobacter spec. sorbed amounts of atrazine comparable to the other species investigated, whereas cell aggregates, formed a few months after isolation, sorbed an order of magnitude less. A large portion of atrazine accumulated by the bacteria could be rapidly desorbed. A remainder of 10% was bound byCytophaga spec. andPseudomonas fluorescens. Acinetobacter spec. bound 70–80% of the atrazine sorbed. In the range of 0.3–3 mg/L atrazine, there was a linear relationship between the amount of non desorbable herbicide and its concentration in the incubation medium.